1. Field of the Invention
This invention relates to the field of electrical interconnecting systems. More particularly it relates to an integrated circuit operational or test socket incorporating a shielding layer in the socket to enhance noise immunity by absorbing and dissipating stray radiated electromagnetic energy (EMI).
2. Description of the Prior Art
Electromagnetic Interference (EMI) is a source of noise which can disrupt normal operation of electronic systems. Sources of EMI can include computer systems and electromechanical devices, and may also include signals from cellular phones, television or radio. Sources of EMI can also include cabling, power supplies, and integrated circuit boards. Electronic devices, such as computers, often generate high frequency signals and radiate electrical noise, which can couple to other electronic devices. EMI may leak out of or into interconnecting and multi-pin connectors or integrated circuit sockets used to couple integrated circuit devices to the integrated circuit boards within the electronic devices. As the device switching speed performance and power dissipation requirements for electronic devices used within computer systems continues to increase, the ability of the interconnecting and multi-pin connectors or integrated circuit sockets to provide high noise immunity during operation continues to decrease. The result is that the interconnecting and multi-pin connectors or integrated circuit sockets are not only increasingly susceptible to externally generated EMI, but are increasingly prolific sources of EMI as well.
Many attempts have been made in the prior art to improve EMI performance of computer systems. Shielding has been utilized which consists of extensive and cumbersome metallic elements having conduits for cables. The shielding elements are typically placed in close proximity to and surrounding the socket or the fixture. While this approach is effective, it is also bulky and expensive to implement. This approach, by incorporating the shielding elements, may also add substantial weight to a system. This is a concern for the avionics industry, where the size and weight of systems must be held to a minimum. A disadvantage with this approach however is that it attenuates EMI from external sources, and is wholly ineffective against EMI from internal proximal sources, such as between the terminals of a device.
Another approach for providing an EMI filter is shown in U.S. Pat. No. 5,528,205, issued Jun. 18, 1996, to Wong, which teaches an integrated and drop-in EMI filter which is made out of a ferrite material. The ferrite material has a cutaway space region configured to define a conductor winding portion and a through hole region configured to allow electrical conductors to pass through. Although this approach does filter EMI from externally generated sources, it has the disadvantage of being difficult to assemble and manufacture due to the construction of the winding. This approach may not be easily adapted to be integrated circuit device socket and would not provide proximally located shielding between individual conductor pins with the socket.
Another approach for providing filtering is seen in U.S. Pat. No. 4,761,147, issued Aug. 2, 1988 to Gauthier. Gauthier teaches a ferrite plate placed within the inner space formed by the front and rear shells of a multi-pin connector. This approach also filters EMI from externally generated sources. This approach has the ferrite plate connected to a point of reference potential to dissipate EMI coupled to the pins of the connector, but does not provide proximal shielding between connectors to prevent the EMI from being coupled to the connectors in the first place, and may not be easily adapted to an integrated circuit test socket.
Yet another approach is seen in U.S. Pat. No. 5,360,353, issued Nov. 1, 1994, to Kinoshita. Kinoshita teaches a concave portion being formed on the surface of a connector body, wherein an EMI filter array is fitted to the concave portion to be inserted between and connected to the contact terminals. This approach, however, is not integrated within the socket itself and requires an external element. This approach also does not provide proximal shielding between connectors to prevent EMI from being coupled to the connectors, and would not be easily adapted to an integrated circuit test socket.